canvas getContext , onload

Question

I have problem with canvas - method getContext.

Code returns error: Can not read property 'getContext' of null.

I think that the reson is not full load html document. When I make this code on my laptop I only need to put:

<script type = "text / javascript" src = "script.js"> </ script>

behind canvas tag but when I copy code to playground sololearn it doesn't work, any easy solution?

Answer 1

sololearn requires a window.onload=function(){
//insert code here
}
ritual.

Answer 2

Dawid
https://code.sololearn.com/WeiZ53LVr02E/?ref=app

Answer 3

Make sure that js its loaded AFTER html

Answer 4

Thanks Brainsng but I thried already that:

window.onload = function(){}

and body onload

leads to lack of access to several functions. In html I have 3 button with onclick that starts functions. When I close this functions in another I lose access.

Answer 5

Dawid Post your code if want more help

Answer 6

https://code.sololearn.com/W58BQlUX0PRV

Answer 7

Functions definition aparts, clock its drawed like expected

Answer 8

KrOW - Yes, with window.onload, but functions "start","stop","reset" doesnt works.

Answer 9

Thanks, Brainsng - I put all on function not only:

window.onload = function(){
var canvas = document.getElementById("canvas");
context = canvas.getContext("2d");

schwimmer1 = 0;
schwimmer2 = 15;
schwimmer3 = 30;
schwimmer4 = 45;

drawClock();
}